Experience in the demagnetization of large objects

The residual magnetization of parts may cause negative effects: in aircraft, it yields a substantial compass error and the unexpected actuation of automatic elements, while during electrical welding on major pipelines, it does not allow one to obtain a high-quality weld. The designs, techniques, and devices intended for demagnetization of large objects, which are difficult to demagnetize using conventional means, are proposed.     

Dependence of the Detectability of Flaws on the Distribution of the Magnetizing Field in the Vicinity of a Flaw

It is shown that the flaw detectability of the magnetic-powder inspection method depends on the ratio of the normal H _n and tangential H _t components of the field in the flaw's vicinity and that H _n/H _t < 3 is a condition that ensures the detectability of surface flaws.     

Effect of the decay rate of a magnetizing field on the detection of flaws in the presence of residual magnetization

An increase in the decay rate of a magnetizing field (to 0.01 s) favors the adequate detection of surface flaws in comparison with the slow (0.5–6 s) field decay (slow current cut-off). The circuitry of a power unit for a flaw detector, which allows the realization of the required rate of reduction, is suggested.Translated from Defektoskopiya, Vol. 40, No. 7, 2004, pp. 53–61.Original Russian Text Copyright © 2004 by Shelikhov.     

The Effect of Coagulation of Magnetic Particles on the Detectability of Flaws in Magnetic-Powder Inspection

Results of studying the influence of magnetic coagulation of magnetic-ink particles on the sensitivity of magnetic-powder inspection are reported. Recommendations on the composition and concentration of magnetic inks are given.     

On the improvement of examination questions during the nondestructive testing of magnetic powder

The most substantial shortcomings of examination questions used in the training and certification of NDT personnel are considered.     

Portable flaw detectors for magnetic-powder inspection of objects under operating conditions

The performance specifications and the use of magnetic-powder flaw detectors under the operating conditions of objects are considered.     

Advantages and shortcomings of magnetic-powder methods for the inspection of parts

The distinctive features, advantages, and shortcomings of magnetic-powder methods for the inspection of parts in an applied magnetic field and by remanent magnetization were analyzed.     

Low-firing binders from magnesium containing carbonate raw materials

This paper presents scientific and experimental data for low-firing hydraulic binders: hydraulic lime and Roman cement based on local mineral raw materials. The binders were prepared by firing representative samples of carbonate–clay magnesian raw materials from Tatarstan. Using X-ray diffraction, we identified the firing products, including a hydraulically active phase, and determined the structural characteristics of its minerals. The compositions of the binders were determined as functions of firing conditions. We examined the influence of the firing temperature and duration of magnesian raw materials in the preparation of binders on MgO activity and demonstrated for the first time the possibility of ensuring an active state of the MgO resulting from firing (up to 21%) and suppressing its negative effect on Roman cement and hydraulic lime hardening processes.